Schiller Martin, Bizzarro Martin, Siebert Julien
Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen, Denmark.
Institut de Physique du Globe de Paris, Université Sorbonne Paris Cité, 75005 Paris, France.
Sci Adv. 2020 Feb 12;6(7):eaay7604. doi: 10.1126/sciadv.aay7604. eCollection 2020 Feb.
Nucleosynthetic isotope variability among solar system objects provides insights into the accretion history of terrestrial planets. We report on the nucleosynthetic Fe isotope composition (μFe) of various meteorites and show that the only material matching the terrestrial composition is CI (Ivuna-type) carbonaceous chondrites, which represent the bulk solar system composition. All other meteorites, including carbonaceous, ordinary, and enstatite chondrites, record excesses in μFe. This observation is inconsistent with protracted growth of Earth by stochastic collisional accretion, which predicts a μFe value reflecting a mixture of the various meteorite parent bodies. Instead, our results suggest a rapid accretion and differentiation of Earth during the ~5-million year disk lifetime, when the volatile-rich CI-like material is accreted to the proto-Sun via the inner disk.
太阳系天体之间的核合成同位素变化为类地行星的吸积历史提供了见解。我们报告了各种陨石的核合成铁同位素组成（μFe），并表明唯一与地球组成匹配的物质是CI（伊武纳型）碳质球粒陨石，它代表了太阳系的整体组成。所有其他陨石，包括碳质、普通和顽火辉石球粒陨石，都记录了μFe的过量。这一观察结果与通过随机碰撞吸积使地球长期生长的情况不一致，随机碰撞吸积预测μFe值反映了各种陨石母体的混合物。相反，我们的结果表明，在约500万年的星盘寿命期间，地球经历了快速吸积和分化，此时富含挥发性物质的类CI物质通过内盘被吸积到原太阳。
